Pre-boil est. is spot on but Post-boil is not?

[WaveFanatic]

Hi everyone,

I have done a few brews now and accepted that the efficiency with my equipment is around 58-65 or so. What I have been baffled with is I usually hit my est. pre-boil OG, but my post boil is 3-7 points off on the low side. What could cause this? I do BIAB, one vessel mash and boil. Water levels post boil is spot on, even lower sometimes. Used a refractometer and hydrometer to confirm and they both show about the same gravity values.

Fairly new to the hobby and loving it.

Thanks for any suggestions..

 

[Blackmuse]

Okay - a couple of questions to help...

1. Have you set up an Equipment profile yet?
2. How many brews? and what efficiency were you set to on each brew? The same or different?
3. How much kettle trub are you leaving behind? Is it consistent?
4. Are the water levels pre-boil the same?

Recommendation for your next few batches: Now that you've done a few (diiferent?) brews I would the most basic of them and use it as a basis for consistency. I know @Nosybear would agree with this - brew the same basic recipe (typically a blonde ale) over and over to hone in your process/equipment. That's what he recommended for me and it helped tremendously.

 

[Ward Chillington]

Here's a couple of things to look at as maybes.......Altitude, Relative Humidity, how vigorous is your boil could be part of your "Water levels post boil is spot on, even lower sometimes. " quandary , as to the readings...are you adjusting your hygro and refracto meters for temperature? Cooling down a sample of mash wort from 150°F is much faster then for sweet wort from boiling.

Also, 5 to 7 point delta? Relax, don't worry.....and welcome to Brewer's Friend! Good first post!

 

[WaveFanatic]

Thanks for the reply.

1. Yes I have, but maybe I did not set it right. My batches are 4-2 gallons and use a different brew pot for the 2 gallon brews, but still use the same equipment profile. Both brew pots have the same lower OG values.
2. I have done about 6 brews on my setup. All different recipes. I set the recipe to 65% as a baseline. Only compared the pre-boil to post on maybe 3 brews, trying to improve efficiency.
3. I'm a cheapskate and put everything in the kettle to the fermenter. I updated my equipment profile for no trub loss
4. I sparge the brew bag with cold water to bring up the water from pre-boil, to begin the boil. Gravity measurement is taken before heating for the boil. Temp reading are taken to account for hydometer adjustments.

Will do a SMASH recipe next brew day to dial-in my equipment profile...

 

[Ward Chillington]

4. I sparge the brew bag with cold water to bring up the water from pre-boil, to begin the boil. Gravity measurement is taken before heating for the boil. .

Please expand on this.....and explain at exactly what points in the process you are taking your readings....

 

[WaveFanatic]

I'm in San Diego, so altitude should not be a factor, IMO. The bigger pot though has a less vigorous boil. I really need to get a better propane stove or go electric.

Don't really worry about it, but was just baffled why I was getting the discrepancies. Heck, another pound of grain to get the proper OG is cheap enough.

Thanks

 

[WaveFanatic]

Please expand on this.....and explain at exactly what points in the process you are taking your readings....

For Pre-boil, I take measurements after mixing the sparge/top off water addition.
For Post-boil, measurements are take after chilling the wort or from the fermenter before pitching.

 

[Blackmuse]

Thanks for the reply.

1. Yes I have, but maybe I did not set it right. My batches are 4-2 gallons and use a different brew pot for the 2 gallon brews, but still use the same equipment profile. Both brew pots have the same lower OG values.
2. I have done about 6 brews on my setup. All different recipes. I set the recipe to 65% as a baseline. Only compared the pre-boil to post on maybe 3 brews, trying to improve efficiency.
3. I'm a cheapskate and put everything in the kettle to the fermenter. I updated my equipment profile for no trub loss
4. I sparge the brew bag with cold water to bring up the water from pre-boil, to begin the boil. Gravity measurement is taken before heating for the boil. Temp reading are taken to account for hydometer adjustments.

Will do a SMASH recipe next brew day to dial-in my equipment profile...

1. I usually build a new profile for a separate volume and kettle. I'd make a new profile for whichever you don't have one for.
2. I too, will have conflicting pre-boil readings and have taken to focusing on the final reading and how to improve it. - Setting yourefficiency to 60 or 62 might help bring closer to hitting the final. - Whichever you set it to, don't change it again until you can get an average from your next few batches.
3. Totally fine as far as I can see. Good call on updating the profile to reflect. This too may help...
4. solid.

Hmmm.... Switching from 4 to 2 gallon batches would partially (or mostly) explain the 58-65% gap.
Continue to focus on nailing the final volume - it sounds like your boil off rate is pretty consistent...
I can't explain why you can hit pre-boil but not post... Then again, I've had the same problem... I've even been high pre-boil but then fail to reach the post-boil... Never by much but enough to irk me. I always thought I was maybe doing something wrong...
Do you put in your temperature to allow for expansion when entering the pre-boil volume?

Anyone else have ideas? - I'll try and keep good tabs on mine over the next couple brews and see what I notice on my end.

 

[Blackmuse]

For Pre-boil, I take measurements after mixing the sparge/top off water addition.
For Post-boil, measurements are take after chilling the wort or from the fermenter before pitching.

These are the same points I take mine too.

 

[WaveFanatic]

Then again, I've had the same problem... I've even been high pre-boil but then fail to reach the post-boil... Never by much but enough to irk me. I always thought I was maybe doing something wrong...
Do you put in your temperature to allow for expansion when entering the pre-boil volume?

OK, at least I'm not the only one that has seen the discrepancy. Not sure what you mean on your question. Put in the temp where? Still a newbie on using BF..

Thanks..

 

[Blackmuse]

See "Total Water Volume in Mash" and then to the far right is the "temperature correction"---- this option comes up on each brew log entry. Since water expands when it heats up you may think you have more than is there. For instance, I top up to 7 gallons for boil size but with temperature correction I typically have 6.8 gallons.

 

[Megary]

I also brew BIAB. My pre-boil gravities are always higher than predicted by the software (usually by 6-8 points!) but my OG’s (post-boil gravities) are usually spot-on or within a point or 2 of what was expected.

My guess is that the problem lies in your grain crush. Crush a little finer or crush twice and I bet you’ll be right where you want to be.

Cheers!

 

[WaveFanatic]

I also brew BIAB. My pre-boil gravities are always higher than predicted by the software (usually by 6-8 points!) but my OG’s (post-boil gravities) are usually spot-on or within a point or 2 of what was expected.

My guess is that the problem lies in your grain crush. Crush a little finer or crush twice and I bet you’ll be right where you want to be.

Cheers!

Cool, definitely not just me then. Could be an algo thing too.

I use a corona mill, so definitely crushing fine. You really have no choice but "rough" fine crush on a corona and BIAB. Learned that from my first few brews, and research..

Thanks everyone for the insight, to a really minor annoyance.. OG is what to concentrate on..

 

[Ward Chillington]

What's with the sparging with cool water? Is that a BIAB thing?

 

[WaveFanatic]

Not really. I pour cold water into the bagged grain while on a colander, so I can squeeze it more. Trying get more sugars out, instead of just topping off the kettle with plain water.

 

[Nosybear]

Not really. I pour cold water into the bagged grain while on a colander, so I can squeeze it more. Trying get more sugars out, instead of just topping off the kettle with plain water.

That's a reasonable approach but just a tip: Hot (170 degree F) water would get more of the sugars than cold water. You're going to boil the wort anyway so why not give it a bit of a head start?

 

[Craigerrr]

That's a reasonable approach but just a tip: Hot (170 degree F) water would get more of the sugars than cold water. You're going to boil the wort anyway so why not give it a bit of a head start?

That is a good point Nosy. I guess it is the same reason we use hot water to wash dishes, clothes, and brewing equipment for better cleaning.

 

[^Tony^]

I don't sparge with my BIAB. I lose about 2 litres (1/2 gallon) per 5.5 kg (12 lbs) of grist AS (after squeeze)

At the end of the mash I remove my bag and let it drain until its slowly dripping then squeeze the crap out of it. Then my boil takes another 4 L (1 gallon) out. I use the fermenter volume in the recipe builder to calculate the starting volume pre-mash (about 32 L /8.5 gal) which gives me between 24-26.5 L (6.5-7 gal) in the fermenter if I am being generous including trub. I'm usually a little low on my pre-boil gravity but usually over by a few points on my post-boil gravity but I take that into account (a little bit) when I build the recipe.

I used to spend an hour calculating out sparge volumes and final and such. In the end sparge VS no sparge...my no sparge method made no difference in the final beer quality compared to sparging so I cut out the extra time and hassle of the sparge. Saves me time and effort.

EDIT: I mill my grains fairly well and I have been hitting mid-70's % efficiency with no sparge.

 

[WaveFanatic]

That's a reasonable approach but just a tip: Hot (170 degree F) water would get more of the sugars than cold water. You're going to boil the wort anyway so why not give it a bit of a head start?

I will definitely give that a go on my next brew day. Just been doing cold water so I can squeeze the bag comfortably, but will bust out some gloves for some hot squeezing action.

 

[WaveFanatic]

I used to spend an hour calculating out sparge volumes and final and such. In the end sparge VS no sparge...my no sparge method made no difference in the final beer quality compared to sparging so I cut out the extra time and hassle of the sparge. Saves me time and effort.

EDIT: I mill my grains fairly well and I have been hitting mid-70's % efficiency with no sparge.

Hmm.. So just calculate for a thinner mash and do away with the extra sparge step to top off. May take a bit more practice to get the right volume, but I'm open to that too. It may only work out on my bigger kettle though.

Thanks everyone..